JP6059389B1 - Melting control method for fast induction melting furnace - Google Patents

Abstract

Disclosed is a melting control method for a high-speed induction melting furnace capable of suppressing deterioration in quality of an alloy even when a material to be heated is melted at high speed in a short time. A melting control method of a high-speed induction melting furnace includes an applied electric power P and a frequency f applied to a heating coil 61, (1) a molten metal stirring force F of the material to be heated, and a coating on the molten metal surface in the molten metal. A first condition that is not caught in, (2) a second condition that suppresses the frequency f from being scattered on the surface of the molten metal, and (3) a frequency f that suppresses self-heating of the furnace wall. (4) The molten metal stirring force F is calculated using a fourth condition that is defined as a relational expression including at least the applied power P and the frequency f. [Selection figure] None

Description

  The present invention relates to a melting control method for a high-speed induction melting furnace in which high-frequency power is supplied to a heating coil provided on the outer periphery of a furnace wall through power supply means to rapidly melt a material to be heated stored in the furnace.

  Conventionally, as this type of induction melting furnace, as shown in the following Patent Document 1 by the present applicant and the present inventors, electric power is supplied to a heating coil provided on the outer periphery of the furnace wall via electric power supply means. There is known an induction melting furnace for melting a material to be melted stored in the furnace.

  As a pioneer of research and development of induction melting furnaces, the present applicant and the inventor control the stirring force generated in the molten metal in the second stage in which the component adjusting material is added to the molten material to be melted in the following Patent Document 1. And the control signal of the frequency suitable for making a component adjustment material melt | dissolve in to-be-melted material is produced | generated.

Japanese Patent No. 5656532

  Here, when aluminum or magnesium is melted at a high speed in a short time and supplied to the die casting machine, the quality of the aluminum alloy or magnesium alloy is deteriorated by, for example, entraining the surface oxide film with the stirring force of the molten metal. It was common sense in the die casting industry that it was not suitable as a method for supplying to die casting machines.

  The applicant and the inventor, who are pioneers in the research and development of induction melting furnaces, lead to deterioration of the quality of the alloy due to the inclusion of an oxide film on the surface by the stirring force of the molten metal, while repeating intensive testing and research. As a factor, the inventors have found that a stirring force suitable for die casting can be generated by paying attention to the inclusion number K value.

  The present invention is based on such knowledge, and an object of the present invention is to provide a melting control method for a high-speed induction melting furnace that can suppress deterioration in quality of an alloy even when a material to be heated is melted at high speed in a short time. And

According to the first aspect of the present invention, there is provided a melting control method for a high speed induction melting furnace in which a high-frequency power is supplied to a heating coil provided on the outer periphery of the furnace wall via a power supply means to quickly store a material to be heated stored in the furnace. Is a melting control method for a high speed induction melting furnace that melts at high speed.
The applied power P and frequency f applied to the heating coil are
(1) The first condition that the molten metal stirring force F of the heated material is such that the coating on the molten metal surface is not involved in the molten metal,
(2) a second condition that suppresses the frequency f from scattering on the surface of the molten metal of the heated material;
(3) The frequency f is satisfied so as to satisfy a third condition for suppressing self-heating of the furnace wall.
(4) The molten metal stirring force F is calculated using a fourth condition defined as a relational expression including at least the applied power P and the frequency f.

  According to the melting control method for a high speed induction melting furnace of the first invention, the applicant and the inventor who are pioneers in research and development of induction melting furnaces pay attention to the number K of inclusions which is a quality evaluation value of the alloy. Thus, the present inventors have found that there is a proportional relationship between the inclusion number K value and the stirring force, and it is necessary to generate the stirring force at which the inclusion number K value becomes the quality level value.

  Based on this knowledge, the applied power P and the frequency f applied to the heating coil are set to (1) the molten metal stirring force F of the material to be heated as the first condition in which the coating on the molten metal surface is not caught in the molten metal. Thus, the quality of the alloy can be ensured.

  Further, the condition of the molten metal stirring force is defined as (4) a relational expression between the applied power P and the frequency f using a fourth condition that defines the molten metal stirring force F as a relational expression including at least the applied power P and the frequency f. Can be calculated.

  Further, (2) the frequency f satisfies a second condition for suppressing scattering of the molten metal surface of the heated material, and (3) the frequency f satisfies a third condition for suppressing self-heating of the furnace wall. By doing so, a specific operation by an induction melting furnace can be made possible.

  With the applied voltage P and the frequency f thus determined, the quality of the alloy can be suppressed even when the material to be heated is melted at high speed in a short time.

The melting control method of the high speed induction melting furnace of the second invention is the first invention,
(1) The first condition is that the molten metal stirring force F is smaller than the upper limit stirring force F1,
(2) The second condition is that the frequency f is larger than the lower limit frequency f2.
(3) The third condition is that the frequency f is smaller than the upper limit frequency f3.
(4) The fourth condition is as follows:

It is represented by.

  According to the melting control method for a high speed induction melting furnace of the second invention, the first to fourth conditions can be specifically set. With the applied voltage P and the frequency f thus determined, even when the material to be heated is melted at high speed in a short time, it is possible to specifically suppress the deterioration of the alloy quality.

The melting control method of the fast induction melting furnace of the third invention is the second invention,
By the first and fourth conditions, the following formula is satisfied

And f2 <f <f3 according to the second and third conditions.
It is characterized by satisfying.

  According to the melting control method of the high speed induction melting furnace of the third invention, the relational expression between the applied voltage P and the frequency f that should be specifically satisfied by the first and fourth conditions can be set. Further, it is possible to set a conditional expression of the frequency f that should be specifically satisfied from the second and third conditions. With the applied voltage P and the frequency f thus determined, even when the material to be heated is melted at high speed in a short time, it is possible to specifically suppress the deterioration of the alloy quality.

According to a fourth aspect of the present invention, there is provided a melting control method for a high speed induction melting furnace according to the third aspect of the present invention,
The applied power P and the frequency f applied to the heating coil are further satisfied so that (5) the applied power P also satisfies the fifth condition that the lower limit applied power P5 or more.
A region of the frequency f and the applied power P that satisfies the first to fifth conditions is represented on a map, and the frequency f and the applied power P in the region can be arbitrarily selected.

  According to the melting control method of the high speed induction melting furnace of the fourth invention, the applied voltage P and the frequency f satisfying the first to fourth conditions can be developed on a plane map having these as axes. By setting the lower limit applied power P5 of the condition, it is possible to set a region on the map of the applied power P and the frequency f satisfying the first to fifth conditions.

  Thus, the applied voltage P and the frequency f obtained as a closed region on the map can specifically suppress the deterioration of the quality of the alloy even when the material to be heated is rapidly melted in a short time. .

According to a fifth aspect of the present invention, there is provided a melting control method for a high speed induction melting furnace according to the fourth aspect of the present invention,
The upper limit stirring force F1 of the first condition is defined in a stepwise manner in consideration of the upper limit stirring force F2 that suppresses scattering of the molten metal surface of the heated material, and the frequency f and the applied power P in the region are stepped. It can be arbitrarily selected.

  According to the melting control method of the fast induction melting furnace of the fifth invention, the closed region on the map satisfying the first to fifth conditions can set the first to fifth conditions stepwise. However, by defining the upper limit stirring force F1 of the first condition stepwise while considering the upper limit stirring force F2 that suppresses the scattering of the molten metal surface of the material to be heated, the frequency f and the applied power P in the region are stepped. It can be arbitrarily selected.

  In this way, the applied voltage P and the frequency f obtained stepwise as a closed region on the map specifically suppress the deterioration of the alloy quality even when the material to be heated is rapidly melted in a short time. be able to.

In any one of the first to fifth inventions, the melting control method for the high speed induction melting furnace of the sixth invention,
From the mass of the material to be heated and the specific heat, an integrated power amount for heating the material to be heated to a desired temperature is calculated.

  According to the melting control method of the high speed induction melting furnace of the sixth aspect of the present invention, by determining the applied power P and the frequency f applied to the heating coil, the material to be heated is set to a desired temperature from the mass and specific heat of the material to be heated. It is also possible to calculate the integrated power amount when heating at the same time. Thereby, by determining whether or not the integrated power amount has been applied, it is possible to determine the end of melting, while suppressing deterioration in the quality of the alloy even when the material to be heated is melted at high speed in a short time, The material to be heated can be surely dissolved.

The whole block diagram which shows the structure of an induction melting furnace. Explanatory drawing which shows the processing content of a control circuit.

  With reference to FIG. 1, an example of the fast induction melting furnace of this embodiment is demonstrated. Note that the high speed induction melting furnace is not limited to this, and may have other configurations as long as it is a high frequency power supply facility.

  The high-speed induction melting furnace melts the material to be heated X stored in the melting furnace. Specifically, the power source 1, the high-voltage power receiving panel 2, the converter transformer 3, and the power converter. 4, a high-frequency matching device 5, an induction heating device 6, and a controller 100.

  The power source 1 is an AC power source and is connected to the high voltage power receiving panel 2.

  The high-voltage power receiving panel 2 is a device for energizing / stopping the power to the induction heating device 6 and shutting off the power when a failure occurs, and includes a power fuse 2a and a circuit breaker 2b. The power fuse 2a is a means for interrupting current in the event of a short circuit accident, and the circuit breaker 2b performs an opening / closing operation associated with energization and stop of the power source.

  The transformer for converter 3 is connected to the high voltage power receiving panel 2 and adjusts so that the input voltage to the power converter 4 becomes a predetermined value.

  The power conversion device 4 is a device for generating an arbitrary high-frequency current from a commercial power supply of 50 Hz or 60 Hz, connected to the transformer 3 for the conversion device, and is a control circuit 10 and an AC / DC converter. Converters 41a and 41b and inverse converters 42a and 42b, which are DC / AC converters, are controlled by an output control signal from the control circuit 10.

  Specifically, the power converter 4 includes diode type forward converters 41a and 41b on the input side, IGBT type reverse converters 42a and 42b on the output side, and a smoothing reactor in series with the forward converters 41a and 41b. 43a is connected, and a smoothing capacitor 44 is connected in parallel to the forward converters 41a and 41b.

  Furthermore, the power conversion device 4 includes a DC voltage detector 45 that detects a DC voltage on the output side of the forward converters 41a and 41b and outputs a DC voltage signal (a). The output value of the DC voltage detector 45 is Are output to the control circuit 10.

  Details of the control content of the power conversion device 4 by the control circuit 10 will be described later.

  The high-frequency matching device 5 is provided between the power conversion device 4 and the induction heating device 6 and improves the load power factor because the induction heating device 6 has a low power factor.

  Specifically, the high-frequency matching device 5 detects and outputs the resonance capacitors 51a and 51b, the current detector 52 that detects the output current of the high-frequency matching device 5 and outputs the output current signal (d), and the output voltage. The voltage detector 53 is configured to output a voltage signal (e).

  The induction heating device 6 generates an eddy current in the material X to be heated housed in the melting furnace body by energizing the heating coil 61 with a high-frequency current supplied from the power conversion device 4 and the high-frequency matching device 5. The material to be heated X is heated and melted by Joule heat generated by eddy current.

  The controller 100 controls the overall operation of the induction melting furnace including the operation / stop of the control induction melting furnace.

  Next, the control circuit 10 that will be described later will be described.

  The control circuit 10 mainly performs control such as output adjustment, and as a control device for the induction melting furnace, has a function as a control signal generation unit that controls the IGBT inverters 42a and 42b. A melting control method is performed in which the material to be heated X accommodated in the furnace is rapidly melted in a short time by supplying high-frequency power to the furnace.

Specifically, the control circuit 10 determines the applied power P and the frequency f applied to the heating coil 61 according to the material to be heated X,
(1) The first condition that the molten metal stirring force F of the heated material is such that the coating on the molten metal surface is not involved in the molten metal,
(2) a second condition that suppresses the frequency f from scattering on the surface of the molten metal of the heated material;
(3) The frequency f is satisfied so as to satisfy a third condition for suppressing self-heating of the furnace wall.
(4) The molten metal stirring force F is calculated using a fourth condition defined as a relational expression including at least the applied power P and the frequency f.

More specifically,
(1) The first condition is that the molten metal stirring force F is smaller than the upper limit stirring force F1. For example, when the material X to be heated is an aluminum alloy, the number K of inclusions that determines the quality of the aluminum alloy is proportional to the number K of inclusions, for example, to be less than 0.9. An upper limit stirring force F1 of the molten metal stirring force F is determined. For example, in this case, F1 = 43.1 [kg / cm 2].
(2) The second condition is that the frequency f is greater than the lower limit frequency f2. For example, when the material X to be heated is an aluminum alloy, f2 = 8000 [Hz]. When the temperature is less than this, the molten metal stirring force F becomes excessively large and the molten metal can be scattered.
(3) The third condition is that the frequency f is smaller than the upper limit frequency f3. For example, when the material to be heated X is an aluminum alloy, f3 = 10000 [Hz]. When the temperature is higher than this, the furnace itself (the crucible itself) is heated, and the crucible may be broken by a heat shock. There is sex.
(4) The fourth condition is

It is represented by

  Furthermore, the following equation is satisfied by the first and fourth conditions.

That is, in the case of the above aluminum alloy,

It becomes.

On the other hand, according to the second and third conditions, f2 <f <f3
That is, in the case of the aluminum alloy,
8000 [Hz] <f <10000 [Hz]
Thus, the applied power P and the frequency f satisfying these two are calculated.

  Furthermore, in addition to the first to fourth conditions described above, (5) considering the fifth condition that the applied power P is equal to or higher than the lower limit applied power P5, the frequency f and the applied power P satisfying the first to fifth conditions Can be represented on the map.

  For example, in the case of the above aluminum alloy, P5 = 20 kW, and the fifth condition in this case is P ≧ 20 kW.

  Specifically, as shown in FIG. 2, a region (region (I) in the figure) between the frequency f and the applied power P satisfying the first to fifth conditions can be represented on the map, and the control circuit 10 Can arbitrarily select the frequency f and the applied power P in the region (I).

  Furthermore, on the map, the upper limit stirring force F1 of the first condition can be defined in a stepwise manner in consideration of the upper limit stirring force F2 that suppresses the scattering of the molten metal surface of the heated material X.

  The upper limit stirring force F2 and the fourth condition satisfy the following formula

That is, in the case of the above aluminum alloy, F2 = 54.5 [kg / cm2],

In the region (II) of FIG. 2, the region (I) is defined as a region that can suppress the scattering of the molten metal surface of the material X to be heated (the quality does not have an inclusion number K value of 0.9 or less). As the spare area, the frequency f and the applied power P can be set stepwise with respect to the area (I).

  Here, the frequency f and the applied power P are determined from the region (I) as follows.

  First, as the frequency f increases, the power concentrated on the alloy surface increases and the Joule heat due to the specific resistance of the material X to be heated also increases. Therefore, the smaller the bulk size of the material to be heated X, the larger the surface area and the higher the heating efficiency. On the other hand, when the bulk size of the material to be heated X is large, current concentrates only on the surface and heating does not proceed to the inside of the material, so that the melting ability is lowered.

  Therefore, the frequency f is selected to be smaller (f2 side) as the bulk size of the heated material X is larger, and the frequency f is larger as the bulk size of the heated material X is smaller ( Select f3 side).

  Furthermore, the applied electric power P is, for example, in the region (I) when it is necessary to dissolve the material to be heated X in a shorter time in accordance with the production tact time such as it is necessary to complete the melting within several minutes. ) In the range of (), select the high power side (close to region (II)), and if there is time, select the low power side in the range of region (I) (close to P = P5). .

  As described above, the frequency f and the applied power P are determined from within the region (I).

  In addition to determining the frequency f and the applied power P, the control circuit 10 calculates the integrated power amount when heating the heated material to a desired temperature from the mass and specific heat of the heated material X.

  Here, instead of specific heat, as an experimental result formula for raising the aluminum alloy to 680 ° C. which is the melting end temperature at f = 10000 [Hz].

As sought. This is corrected in the molten metal temperature range (560 ° C to 700 ° C),

It was.

  Thereby, from such a calculation formula, the control circuit 10 can determine the end of melting by determining whether or not the integrated power amount has been applied, and reliably control the material to be heated while suppressing excessive melting. Can be dissolved.

  As described above in detail, the material to be heated X is melted at high speed in a short time by supplying the heating coil 61 of the present embodiment with high-frequency power composed of the frequency f and the applied power P satisfying the above conditions. Even in this case, it is possible to suppress deterioration of the quality of the alloy.

  In the present embodiment, the aluminum alloy has been described as an example. However, the material to be heated X is, for example, copper, lead, tin, zinc, magnesium, as long as it can be melted at high speed in a short time and supplied to the die casting machine. Nonferrous metals such as these and alloys thereof may also be used.

DESCRIPTION OF SYMBOLS 1 ... Power supply, 2 ... High voltage receiving board, 3 ... Transformer for conversion apparatuses, 4 ... Power conversion apparatus, 5 ... High frequency matching apparatus, 6 ... Induction heating apparatus, 10 ... Control circuit (control signal production | generation part), 41a, 41b ... diode type forward converter, 42a, 42b ... IGBT type reverse converter, 61 ... heating coil, 100 ... controller, X ... material to be heated.

Claims (6)

This is a melting control method for a high-speed induction melting furnace in which high-frequency power is supplied to a heating coil provided on the outer periphery of the furnace wall via a power supply means to rapidly melt a material to be heated stored in the furnace in a short time. And
The applied power P and frequency f applied to the heating coil are
(1) The first condition that the molten metal stirring force F of the heated material is such that the coating on the molten metal surface is not involved in the molten metal,
(2) a second condition that suppresses the frequency f from scattering on the surface of the molten metal of the heated material;
(3) The frequency f is satisfied so as to satisfy a third condition for suppressing self-heating of the furnace wall.
(4) A melting control method for a high speed induction melting furnace, wherein the molten metal stirring force F is calculated using a fourth condition defined as a relational expression including at least the applied power P and the frequency f. In the melting control method of the fast induction melting furnace according to claim 1,
(1) The first condition is that the molten metal stirring force F is smaller than the upper limit stirring force F1,
(2) The second condition is that the frequency f is larger than the lower limit frequency f2.
(3) The third condition is that the frequency f is smaller than the upper limit frequency f3.
(4) The fourth condition is as follows:
A melting control method for a high-speed induction melting furnace, characterized by: In the melting control method of the fast induction melting furnace according to claim 2,
By the first and fourth conditions, the following formula is satisfied
And f2 <f <f3 according to the second and third conditions.
A melting control method for a high-speed induction melting furnace, characterized in that:
In the melting control method of the high-speed induction melting furnace according to claim 3,
The applied power P and the frequency f applied to the heating coil are further satisfied so that (5) the applied power P also satisfies the fifth condition that the lower limit applied power P5 or more.
A region of the frequency f and the applied power P that satisfies the first to fifth conditions is represented on a map, and the frequency f and the applied power P in the region can be arbitrarily selected. Melting control method for melting furnace. In the melting control method of the high speed induction melting furnace according to claim 4,
The upper limit stirring force F1 of the first condition is defined in a stepwise manner in consideration of the upper limit stirring force F2 that suppresses scattering of the molten metal surface of the heated material, and the frequency f and the applied power P in the region are stepped. A melting control method for a high-speed induction melting furnace, characterized by being arbitrarily selectable. In the melting control method of the high-speed induction melting furnace according to any one of claims 1 to 5,
A melting control method for a high-speed induction melting furnace, wherein an integrated electric energy for heating the material to be heated to a desired temperature is calculated from the mass and specific heat of the material to be heated.